An overturn prevention system has been proposed, which provides at a lower part of an axle box with a stopper device for restraining a vehicle in case of a derailment so that the vehicle is not brought to contact with tracks (rails) and is not displaced in the lateral direction; as a device for preventing a vehicle from overturning in case of derailment due to a natural disaster, such as an earthquake and a gust, by guiding the vehicle to travel on ballast with sleepers or on roadbed, etc. (For example, refer to the Patent Article 1.)
[Patent Article 1] The Japanese Publication Patent No. 3393032